We have the equation of the line in point-slope form is
[tex](y-y_1)=m(x-x_1)[/tex]where
m = slope = -9
(6,-7)=(x1,y1)
we substitute the values
[tex]\begin{gathered} (y+7)=-9(x-6) \\ \end{gathered}[/tex]then we need to isolate y
[tex]\begin{gathered} y+7=-9x+54 \\ y=-9x+54-7 \\ y=-9x+47 \end{gathered}[/tex]the equation of the line is
y=-9x+47